SAE-AISI P21 (T51621) Low-Carbon Mould Steel

SAE-AISI P21 steel is a tool steel. Cited properties are appropriate for the hardened (H) condition. P21 is the designation in both the SAE and AISI systems for this material. T51621 is the UNS number. The graph bars on the material properties cards below compare SAE-AISI P21 steel to: tool steels (top), all iron alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 10⁶ psi

Poisson's Ratio

0.29

Rockwell C Hardness

Shear Modulus

73 GPa 11 x 10⁶ psi

Tensile Strength: Ultimate (UTS)

1130 MPa 160 x 10³ psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Melting Completion (Liquidus)

1450 °C 2650 °F

Melting Onset (Solidus)

1410 °C 2580 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

41 W/m-K 24 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.9 % IACS

Electrical Conductivity: Equal Weight (Specific)

9.0 % IACS

Otherwise Unclassified Properties

Base Metal Price

6.5 % relative

Density

7.9 g/cm³ 490 lb/ft³

Embodied Carbon

2.3 kg CO₂/kg material

Embodied Energy

32 MJ/kg 14 x 10³ BTU/lb

Embodied Water

62 L/kg 7.4 gal/lb

Common Calculations

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

40 points

Strength to Weight: Bending

31 points

Thermal Diffusivity

11 mm²/s

Thermal Shock Resistance

37 points

Alloy Composition

Iron (Fe)Fe		92.1 to 94.2
Nickel (Ni)Ni		3.9 to 4.3
Cobalt (Co)Co		1.1 to 1.3
Manganese (Mn)Mn		0.35 to 0.72
Silicon (Si)Si		0.2 to 0.4
Chromium (Cr)Cr		0 to 0.5
Carbon (C)C		0.18 to 0.22
Vanadium (V)V		0.15 to 0.25
Copper (Cu)Cu		0 to 0.25
Phosphorus (P)P		0 to 0.030
Sulfur (S)S		0 to 0.030